1. FIELD OF THE INVENTION
This invention relates to a dental syringe of the type having a pre-filled cartridge of fluid medication and a double ended hypodermic needle which may be automatically relocated from a distally extended position, at which to inject the fluid medication into a targeted tissue area, to a proximally retracted position, at which the needle is withdrawn into and shielded by the cylinder of the syringe.
2. PRIOR ART
Dental syringes of the type having a pre-filled cartridge of fluid medication and a double ended hypodermic needle are well-known in the art for injecting such medication from the cartridge to a targeted tissue area of a patient. However, at the completion of the injection, the needle is typically locked in an axially extended position projecting outwardly from a distal bore formed through the syringe cylinder.
In some cases, the syringe may be used to treat a patient having a communicable disease. Prior to disposing the syringe, the hypodermic needle is frequently broken or destroyed to prevent reuse. Dental office workers are especially susceptable to accidental and potentially infectious needle strikes due to the careless handling or breaking of the needle and disposing of the syringe after use. The resulting mini-accident caused by an accidental needle strike typically requires a blood test for such diseases as AIDS and hepatitis. The corresponding cost and inefficiency of testing dental office workers who have received such an accidental needle strike result in considerable waste, which may be particularly damaging to a dental facility which is striving for economy.
The following patent applications, which are assigned or will be assigned to the assignee of the present patent application, disclose syringes having a pre-filled medication cartridge and a needle which is retractable within the syringe cylinder: U.S. Pat. No. 4,767,413 issued Aug. 30, 1988 and entitled DENTAL SYRINGE HAVING AN AUTOMATICALLY RETRACTABLE NEEDLE; and application Ser. No. 101,251 filed Sept. 25, 1987 and entitled DISPOSABLE, PRE-STERILIZABLE SYRINGE FOR A PRE-FILLED MEDICATION CARTRIDGE.